Dawn dish detergent is is a good option to use to kill fleas on cats. It has also been effective and safe for use in getting rid of fleas on young kittens.
A pet owner can use Dawn dish detergent just like shampoo on a cat. Running a warm water bath and lathering the cat, allowing the detergent to sit for at least 10 minutes, can begin to kill the fleas. The Dawn dish detergent dries up the insects, destroying their exoskeletons. This drying of the outer shell kills the fleas after a few minutes. Because Dawn dish detergent is a simple detergent, it is not harmful to animals.